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I've had success electroplating $\ce{Ni}$ and $\ce{Cu}$, but interestingly never $\ce{Al}$. My focus here is on plating with $\ce{Au}$, specifically onto an $\ce{Ni}$ surface.

In general from my own work and others' suggestions, I have found applying a voltage (direct current) of 5 V through a relatively dilute solution of relevant metal, e.g. 2.53 g $\ce{Ni(NH4)2(SO4)2*6H2O}$ dissolved in 81.9 mL 0.42 % acetic acid at ~60 °C makes a very nice, lustrous plating of $\ce{Ni}$ on a clean $\ce{Cu}$ surface after ~90 s of submersion.

I have been able to dissolve $\ce{Au}$ in warm, concentrated $\ce{HCl}$ and minimal $\ce{HNO3}$, and have heard that you can dissolve it in $\ce{HCl}$ and $\ce{H2O2}$, which makes sense because $\ce{Cu}$ does the same.

I'm looking for an ideal solution here, starting with pure metallic gold. I want to avoid any mistakes because I only have 1 g to work with. By default I'm going to try a comparable concentration of dissolved $\ce{Au}$ to what I mentioned with $\ce{Ni}$, but any advice is appreciated – especially a specific method for making an "ideal" solution.

I've found that several commercial solutions contain $\ce{(CN)4AuK}$, but I really want to avoid using cyanide.

This paper by Paul A. Kohl is immensely helpful and interesting, but I'm wondering if anyone has had any success with something simple. It makes mention of using sulphide, thiosulfite, thallium, etc.

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The problem is your amount of gold that you have. Normal chemical baths contain several grams per liter. So you will need to operate in small volumes. You can use this article - Chemical Papers June 2012, Volume 66, Issue 6, pp 617-620 Date: 23 Dec 2011 Etching and recovery of gold from aluminum substrate in thiourea solution, that is using thiurea. Be aware of the low stability of this bath. The bath will degrade quite fast, but that is common problem of all non-cyanide gold baths.

As the article deals with a gold dissolution, I would suggest to reduce the gold back to a solid state. Use the article or this Hydrometallurgy Volume 55, Issue 2, March 2000, Pages 137–152, Gold electrowinning from aqueous–alcoholic thiourea solutions and then do the electrodeposition.

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